This proposal is part of the program initiated by Digital Scintigraphics, Inc. to develop a commercially viable single photon emission computed tomography (SPECT) camera employing, for the first time, totally digital position analysis procedures. Current effort is based on the use of an annular crystal offering much higher sensitivity and higher fidelity than available instruments. Other characteristics such as mechanical simplicity, high event rate, and auto-calibration capabilities offer the promise of a camera having significant advantages for clinical studies. The Phase I proposal would involve the development of digital algorithms designed to optimize resolution and uniformity, the finalizing of the optimum crystal size and photomultiplier requirements for a clinical prototype, and the development of computer-controlled calibration procedures. At the completion of Phase I, we will understand the obtainable performance of the laboratory prototype, and how various parameters affect the performance. Detailed knowledge of the tradeoffs involved will enable us to proceed to Phase II of our program, which is the construction of a clinical prototype superior to existing SPECT systems.